UEFA have described as “null, void and unenforceable” any contractual clause which would prevent on-loan Atletico Madrid goalkeeper Thibaut Courtois from playing against parent club Chelsea in the Champions League.
Chelsea and Atletico were drawn to face each other in Friday's semi-final draw.
There had been reports that Chelsea would demand prohibitively expensive payments from Atletico for Courtois to play against them, as per a clause in the contract relating to his loan.
However, a UEFA statement said: “The UEFA Champions League and the UEFA Disciplinary Regulations contain clear provisions which strictly forbid any club to exert, or attempt to exert, any influence whatsoever over the players that another club may (or may not) field in a match.”
UEFA said that it followed that any provision “which might function in such a way as to influence who a club fields in a match is null, void and unenforceable so far as UEFA is concerned.”
UEFA warned that any attempt to enforce such a provision would be a clear violation of the regulation, and would be sanctioned accordingly.